Moore criticised his backline following last weekend's 4-2 defeat to Colchester and admitted he did not realise how bad the problem was.
Under Moore, Tranmere have risen from 19th to 13th in the table and would have moved up to 10th with a win against the U's.
"I didn't think we needed that many defenders but, after seeing that, we obviously do," he told BBC Radio Merseyside.
"For me, that's more of a major concern than trying to find a new striker.
"The players that we're looking for will be the ones that nearly everybody's after."
Any reproduction, publication or redistribution of this material without the written agreement of 365 Media Group is strictly forbidden.